1. Field of the Invention
The present invention relates to a micromechanical device such as packaging of a micro-electro-mechanical-systems, and a method of manufacturing the micromechanical device.
2. Description of the Related Art
As an example of the micromechanical device, Micro-Electro-Mechanical-Systems (MEMS) 101 in which a MEMS element 104 as a micromachine having a motion is mounted on a substrate 102, and is sealed in a hollow state as shown in FIGS. 19 to 21 are known. Such an example is shown in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2005-207959 or U.S. Pat. No. 7,008,812B1.
The MEMS 101 is constituted of a substrate 102, an insulating layer 103, a MEMS element 104, signal wiring 105, drive electrodes 106, a lower electrode 107, a first sealing body 108, and a second sealing body 109, and a hollow section 110 is configured inside. The first sealing body 108 has holes 108a. The MEMS element 104 has a double-supported or cantilever beam structure, in which the beam is formed in such a manner that a gap of several μm is held between a central part of the beam and the signal wiring 105. In the insulating layer 103 directly under the MEMS element 104, the signal wiring 105 is formed by using Au or the like. The MEMS element 104 is constituted of poly-Si or Al having high spring characteristics, and gets closer to the signal wiring 105 side by being given drive force such as electrostatic force or the like.
Further, when the drive force is removed, the MEMS element 104 is restored to the position in which the element 104 has a gap between itself and the signal wiring 105 by its own spring characteristics. By changing the gap between the MEMS element 104 and the signal wiring 105 as described above, the MEMS element 104 performs functions of variable electrostatic capacity, switching, and the like.
In a MEMS 101 of such a type, for the operation and protection of the MEMS element 104, the MEMS element 104 is sealed in a hollow state. The hollow section 110 is a reduced atmosphere.
However, in the technique described above, there has been the following problem. That is, in the MEMS element as a beam-like micromachine, the vibration occurring when the electrostatic force is removed is hard to be settled because of the spring characteristics, which becomes a cause of noise contained in the output signal. Particularly, in the reduced atmosphere of the hollow section, the fluid resistance is small, and hence it is difficult to settle the vibration of the micromachine.
The present invention has been contrived to solve the above problem, and an object thereof is to provide a micromechanical device capable of reducing noise in the output signal by making the vibration of the micromachine easy to be settled, and a method of manufacturing the micromechanical device.